The generation of energy in a clean, renewable and readily available manner is a substantial concern to governments, individuals and research bodies around the world because of the difficulty in securing sufficient fuels to meet rising energy demand and the many environmental hazards associated with the generation of power and the acquisition of fuel stocks. One need only consider the Middle East or the tailpipe of an automobile to begin to appreciate the problems involved with the current approach to energy generation.
Solar energy has for decades been of great interest to scientists and politicians in search of a clean, safe energy supply. It has been estimated that the energy supplied by the Sun to the Earth each year is approximately 3×1024 joules of energy, or 10,000 times more than humanity's current energy use. The ability to harness just a fraction of that energy would create a sea-change in our energy markets and our environmental outlook.
Solar power, however, has not proved the panacea it perhaps at first appeared. Beginning with the Shockley-Queisser limit, first calculated in 1961, scientists have found that the Sun gives up her energy to man—at least for conversion to electricity—rather stubbornly. The history of solar energy is one of expensive manufacturing techniques and low quantum efficiency. Some impressive innovations have occurred though. Professor Gratzel's 1990 dye-sensitized solar cell, for example, showed that the conversion of solar energy to electrical energy could at least be done using inexpensive materials and safe manufacturing processes, albeit at relatively small quantum efficiencies.
There is still, however, a significant need for innovations that improve upon the current techniques used to convert sunlight to electricity. Most efforts directed to developing such innovations have so far been directed toward investigating new materials or manufacturing techniques that would increase the quantum efficiency of solar cells. But these have experienced only limited success, and in any event have heretofore resulted in the use of costly, exotic materials, raising their own environmental concerns, and that are unlikely to improve significantly upon the price per watt of current solar cells or be capable of mass commercialization. While such research may eventually result in useful advances, new directions of innovation are needed.